Three programs are in progress in this laboratory: 1. Our investigation of the crosslinks in collagen is continuing using the enzyme hydrolysis which we have developed into a useful tool recently. A verification of all identified crosslinks and the isolation and identification of possible, completely-reduced crosslinks will also be attempted. In addition we will investigate the formation of crosslinks in elastin using the block polymers poly (Lys-Ala-Ala) and poly (Lys-Ala- Ala-Ala) as models of the crosslinking region in elastin. The crosslinking in these polymers will be investigated by both chemical and enzymatic techniques. 2. Current studies of the acetylation of bone have shown that hyperacetylation of collagen results in peptide bond breaking in alkaline phosphate solutions. Collagen which is closely associated with mineral is protected. In this way, we will be able to dissect away the non-protected collagen and analyze the remaining collagen to determine which portions of the collagen chain are in intimate contact with the mineral. We will also investigate the effect of pre-fracture stress on the mineral:collagen association in normal as well as pathological conditions. 3. Investigations into the mechanism of collagen-induced platelet aggregation have commenced. We will attempt to determine the role, if any, of the collagen:glycosyl transferase activity recently found in platelet membranes. Our approach will be to use whole platelets, collagen and collagen derivatives which are carefully analyzed with regard to the condition of the collagen chain and the carbohydrate moieties. The effectiveness of several types of collagen on platelet aggregation will be determined.